The manganese dioxide/zinc cell in an alkaline potassium hydroxide electrolyte is a widely studied system. However, most of this work has focused on additives to manganese dioxide (MnO2) in order to make this cell rechargeable. To the best of my knowledge, no work has been done so far on the discharge-charge mechanism using microscopic techniques. Hence, with an aim to understand the redox mechanism, the MnO2 cathodes are characterized by transmission electron microscopy (TEM), energy dispersive spectrum analysis (EDS), electron energy loss spectroscopy (EELS) and secondary ion mass spectrometry (SIMS) techniques. The results suggest that the electrode reaction of MnO2 in this electrolyte is potassium (K+) insertion or surface film formation on the surface in addition to the usual protonation i.e. H+ insertion insertion during discharge process. (c) 2008 Elsevier B.V. All rights reserved.